Eisenhower, informally (3)
I believe the answer is:
ike
'eisenhower informally' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for ike that I've seen before include "Thirty fourth US president's nickname" , "Nickname for Dwight Eisenhower" , "Dwight D. Eisenhower, in short" , "Former US President (informally)" , "US general who became president, in short" .)